So I finally changed my plugs and wires.

[iboughtatahoe23]

Pre O2 sensors are up next to the exhaust manifolds and the post are after the cat converters. Pre will have to do with drivability not post. Post is only used to monitor the converters.

I wonder if that y it running lean

 

[Gearz]

Dirty MAF ( Mas Air Flow ) dirty injectors pre O2 sensors fuel pressure etc….. You would need a scan tool or just a parts cannon. LOL

 

[iboughtatahoe23]

Dirty MAF ( Mas Air Flow ) dirty injectors pre O2 sensors fuel pressure etc….. You would need a scan tool or just a parts cannon. LOL

Used a scan tool. I got one. No codes. Runs fine. Cleaned the sensor, cleaned the throttle body. Not sure what else. I use e85. I doubt injectors but maybe?

 

[Fless]

I may have missed it, but what indicates that it's running lean?

Is your engine a flex fuel engine (what's the 8th digit of your VIN), and what kind of short- and long-term fuel trims does the scanner show?

 

[iboughtatahoe23]

I may have missed it, but what indicates that it's running lean?

Is your engine a flex fuel engine (what's the 8th digit of your VIN), and what kind of short- and long-term fuel trims does the scanner show?

It is flex fuel. Not sure on fuel trims. I’ll bust the scanner out tomorrow and look and update you guys.

I thought it was running lean due to these three things I saw on on the plugs:

Some has oil on the threads, some had brick red ash on the tips. And some had white ash on the tips.

8th digit is a 0

 

[Charlie207]

The top end of my 5.3 was not feeling like it was getting enough gas like getting on the highway so at 130k I replaced both pre cat oxygen sensors and the engine woke up like crazy. Oxygen sensors do have a life span and will slowly die without a check engine light. Give it a try if you feel like it’s low on power or your over 100k and you will be surprised what happens!

Also check both the intake manifold gaskets (the seals get hard and will let unmetered air leak into the engine) and the tightness of the intake manifold bolts.

You could hear the air sucking/whistling into the cylinder heads at idle until I torqued the bolts (in sequence) back down. Now it's a semi-regular check, even after new intake manifold gaskets.